BACKGROUND OF THE INVENTION
Field of the Invention
[0001] The present invention relates to a broadband wireless communication system, and in
particular, to an apparatus and a method for controlling a terminal accessing a base
station in a broadband wireless communication system.
Description of the Related Art
[0002] In a 4
th generation (4G) communication system, research for providing services having various
Quality of Service (QoS) using transmission speeds of about 100 Mbps is in active
progress. Particularly, research for supporting high speed services in the form of
guaranteeing mobility and QoS for a broadband wireless access (WBA) communication
system, such as short-distance wireless communication network system and wireless
metropolitan area network (WMAN) system, is in active progress. As an example, communication
systems complying with the Institute of Electrical and Electronics Engineers (IEEE)
802.16 specification is representative of such a system.
[0003] The IEEE 802.16 system standard defines various procedures, such as the operation
of a Media Access Control (MAC) layer. Examples of MAC layer procedures include an
initial ranging procedure and a handover procedure. Described below are procedures
for initial ranging and handover initiated by a terminal in accordance with the IEEE
802.16 system standard.
[0004] The initial ranging procedure according to the IEEE 802.16 system standard is performed
as follows. To initiate initial ranging, a terminal transmits one of a plurality of
prescribed ranging codes to a base station. In response thereto, the base station
transmits a response message RaNGing ReSPonse (RNG_RSP) message to the terminal. The
RNG_RSP message includes ranging status TypeLengthValue (TLV). If the base station
is in a status that does not allow ranging of the terminal (i.e., the entry of the
terminal to the base station), the base station sets the ranging status TLV to "abort"
to inform the terminal of a ranging-not-allowed status. Accordingly, the terminal
detects when its request for entry is not allowed and then scans other base stations
for entry.
[0005] The handover procedure according to the IEEE 802.16 system standard is performed
as follows. To initiate handover, a terminal scans neighboring base stations and transmits
information of scanned neighboring base stations MOBile_Mobile Station HandOver-REQuest
(MOB_MSHO-REQ) message that includes information of target base station candidates
to its serving base station. Accordingly, the serving base station confirms whether
the target base station candidates included in the MOB_MSHO-REQ message received from
the terminal can support service for the terminal. At this point, the serving base
station transmits a MOBile_Base Station HandOver-ReSPonse (MOB_BSHO-RSP) message indicating
that a target base station has been found to the terminal. The MOB_BSHO-RSP message
includes information of the target base station candidates that can provide the requested
handover. The terminal that has received the MOB_BSHO-RSP message selects a target
base station and transmits a MOBile_HandOver-INDication (MOB_HO-IND) message to inform
the serving base station of the selected target base station. The serving base station
that has confirmed the target base station selected by the terminal provides information
regarding the terminal to the target base station, and the terminal performs an entry
procedure to connect to the target base station.
[0006] As described above, the base station can limit entry of the terminal during the initial
ranging procedure. However, the base station cannot prevent the terminal from immediately
trying to access the base station again, that is, retrying the initial ranging procedure.
When the terminal immediately re-requests the base station for entry, there is a high
possibility that the entry request will be denied again since the status of the base
station has not yet changed. Therefore, immediately requesting entry again by the
terminal causes waste of wireless resources. In addition, a terminal that has performed
handover to change the serving base station may initiate handover again to the previous
serving base station. Repeatedly performing handover between two base stations also
causes waste of wireless resources, and repeatedly attempting handover itself wastes
wireless resources. Therefore, there is a need to prevent unnecessary attempts for
entry as well as actual execution of entry procedures.
SUMMARY OF THE INVENTION
[0007] An object of the present invention is to provide an apparatus and a method to prevent
unnecessary attempts for entry and access of a network in a broadband wireless communication
system.
[0008] Another object of the present invention is to provide an apparatus and a method to
prohibit a terminal from attempting re-entry to a specific base station in a broadband
wireless communication system.
[0009] Still another object of the present invention is to provide an apparatus and a method
for informing an entry prohibition time of a specific terminal with respect to a specific
base station in a broadband wireless communication system.
[0010] According to an aspect of the present invention, a base station apparatus in a broadband
wireless communication system includes a controller to determine whether to prohibit
an entry attempt of a terminal, a generator to generate a media access control (MAC)
management message including a value of a timer, the value representing prohibition
of entry attempt, and a transmitter to transmit the MAC management message to the
terminal.
[0011] According to another aspect of the present invention, a terminal apparatus in a broadband
wireless communication system includes a receiver to receive a media access control
(MAC) management message from a base station, a reader to confirm existence of a value
of a timer included in the MAC management message, the value representing prohibition
of entry attempt, and a controller to designate the base station as prohibited for
entry attempt until expiration of the timer.
[0012] According to still another aspect of the present invention, a method for operating
a base station in a broadband wireless communication system includes determining whether
to prohibit an entry attempt of a terminal, generating a media access control (MAC)
management message including a value of a timer, the value representing prohibition
of entry attempt, and transmitting the MAC management message to the terminal.
[0013] According to yet another aspect of the present invention, a method for operating
a terminal in a broadband wireless communication system includes receiving a media
access control (MAC) management message from a base station, confirming existence
of a value of a timer included in the MAC management message, the value representing
prohibition of entry attempt, and designating the base station as being prohibited
from entry attempt until expiration of the timer.
[0014] According to yet another aspect of the present invention, a circuit includes a controller
to determine whether to prohibit entry of an end unit to a base station in a wireless
communication network, the controller configured to process a media access control
(MAC) management message that includes a timer value, the timer value designating
a time period during which entry is prohibited.
[0015] According to yet another aspect of the present invention, a method includes determining
whether to prohibit entry of an end unit to a base station in a wireless communication
network and processing a media access control (MAC) management message that includes
a timer value, the timer value designating a time period during which entry is prohibited.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] The above and other objects, features and advantages of the present invention will
become more apparent from the following detailed description when taken in conjunction
with the accompanying drawings in which:
[0017] FIG. 1 is a view illustrating an example of signal exchange during an initial ranging
procedure in a broadband wireless communication system according to the present invention;
[0018] FIG. 2 is a view illustrating an example of signal exchange during a handover procedure
in a broadband wireless communication system according to the present invention;
[0019] FIG. 3 is a block diagram illustrating a base station in a broadband wireless communication
system according to an exemplary embodiment of the present invention;
[0020] FIG. 4 is a block diagram illustrating a terminal in a broadband wireless communication
system according to an exemplary embodiment of the present invention;
[0021] FIG. 5 is a view illustrating the operating procedure of a base station in a broadband
wireless communication system according to an exemplary embodiment of the present
invention; and
[0022] FIG. 6 is a view illustrating the operating procedure of a terminal in a broadband
wireless communication system according to an exemplary embodiment of the present
invention.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0023] Embodiments of the present invention will be described herein below with reference
to the accompanying drawings.
[0024] Exemplary embodiments of the present invention provide a system and method to prevent
unnecessary attempts for entry and access to a base station by a terminal in a broadband
wireless communication system. For purposes of example, the exemplary embodiments
of the present invention are illustrated in conjunction with a wireless communication
system using an orthogonal frequency division multiple access (OFDMA) scheme. However,
it is to be understood that the present invention may be implemented on wireless communication
systems using other schemes without departing from the scope of the present invention.
[0025] To limit attempts of entry by a terminal, the present invention defines a TypeLengthValue
(TLV) for exchanging entry limit timer information as illustrated in Table 1. The
TLV defined by the present invention may be included in various MAC management messages,
such as RaNGing-ReSPonse (RNG-RSP) messages, Base Station HandOver-REQuest (BSHO-REQ)
messages, and Base Station HandOver-ReSPonse (BSHO-RSP) messages. However, it is to
be understood that the entry limit timer TLV of the present invention may be included
in other messages without departing from the scope of the present invention.
Table 1
Type |
Length |
Value |
Scope |
Xx |
1 |
0-255: In units of 100 milliseconds |
RNG-RSP |
BSHO-REQ |
BSHO-RSP |
[0026] As illustrated in Table 1, a TLV for limiting entry of a terminal according to the
present invention represents a timer value. In an exemplary embodiment, the length
of the TLU is 1 byte, and the value thereof expresses entry limit time in units of
100 milliseconds. When the value is 0, it means that an entry limit time is infinite.
However, it is to be understood that other data lengths and units of time represented
by its value may be used without departing from the scope of the present invention.
For convenience in explanation, the present invention calls the TLV on Table 1 an
"entry limit timer TLV."
[0027] FIG. 1 illustrates an example of signal exchange during an initial ranging procedure
between a terminal and a base station in a broadband wireless communication system
according to an exemplary embodiment of the present invention.
[0028] As shown in FIG. 1, a terminal 110 transmits a ranging request message (e.g., RNG-REQ)
to a base station 120 in order to enter a network (step 101). The base station 120
that has received the ranging request message (e.g., RNG-REQ) recognizes that the
terminal 110 desires to access the base station 120 and determines whether to allow
entry of the terminal 110. Based on the result of the determination step, the base
station 120 may decide that entry to the base station 120 cannot be allowed (step
103). For example, the base station 120 may determine that the entry of the terminal
110 cannot be allowed due to reasons such as resource shortage, service unavailable,
etc.
[0029] In such a situation, the base station 120 transmits a ranging response message (e.g.,
RNG-RSP) that includes an entry limit timer TLV to the terminal 110 (step 105). That
is, the base station 120 transmits the ranging response message (e.g., RNG-RSP) including
ranging status TLV (e.g., ranging status TLV set to "abort") to inform the terminal
of the denial of entry to the base station 120 and an entry limit timer TLV to inform
the terminal of the prohibition of entry to the base station 120 for a predetermined
time. Here, the entry limit timer TLV includes time information prohibiting the entry.
At this point, the base station may also incorporate downlink frequency override TLV
into the ranging response message (e.g., RNG_RSP). The downlink frequency override
TLV includes frequency allocation (FA) information recommended to a terminal designed
to induce the terminal to make an entry request through a different frequency.
[0030] The terminal 110 that has received the ranging response message (e.g., RNG-RSP) including
the ranging status TLV and the entry limit timer TLV recognizes that an entry request
by the terminal 110 has been rejected, and simultaneously, confirms the entry limit
timer TLV to recognize that attempts of entry to the base station 120 is prohibited
for the predetermined time (step 107).
[0031] Accordingly, the terminal 110 does not try entry to the base station 120 for the
predetermined time but rather scans other accessible base stations (step 109). Further,
if the ranging response message (e.g., RNG-RSP) includes the downlink frequency override
TLV, the terminal 110 scans for accessible base stations at the different FA designated
by the downlink frequency override TLV. If, on the other hand, the ranging response
message (e.g., RNG-RSP) does not include the downlink frequency override TLV, the
terminal 110 scans for accessible base stations at the same FA.
[0032] After the scanning step 109, the terminal 110 performs a network entry procedure
again. At this point, even though the base station 120 is determined to be the most
appropriate base station to connect to, i.e., has the best channel status, the terminal
110 does not try entry to the base station 120 while the predetermined time confirmed
in step 107 has not expired.
[0033] FIG. 2 illustrates an example of signal exchange during a handover procedure between
a terminal and a base station in a broadband wireless communication system according
to an exemplary embodiment of the present invention.
[0034] As shown in FIG. 2, a terminal 210 transmits a handover request message (e.g., MOB_MSHO-REQ)
to a serving base station 220 in order to switch (i.e., handover) to an adjacent base
station (step 201). Here, the handover request message (e.g., MOB_MSHO-REQ) may include
information of a target base station 230.
[0035] The serving base station 220 that has received the handover request message (e.g.,
MOB_MSHO-REQ) transmits a handover pre-notification message (e.g., HO_pre_notification)
to the target base station 230 (step 203). The handover pre-notification message (e.g.,
HO_pre_notification) is a message for confirming whether the entry of the terminal
210 can be accepted. The target base station 230 that has received the handover pre-notification
message (e.g., HO_pre_notification) determines whether the entry of the terminal 210
may be accepted and transmits a handover pre-notification response message (e.g.,
HO_pre_notification-RSP) informing the acceptance/denial of the handover request to
the serving base station 220 (step 205).
[0036] If the handover request has been accepted by the target base station 230, the serving
base station 220 that has received the handover pre-notification response message
(e.g., HO_pre_notification-RSP) transmits a base station handover response message
(e.g., MOB_BSHO-RSP) including an entry limit timer TLV to the terminal 210 (step
207). That is, the serving base station 220 transmits the base station handover response
message (e.g., MOB_BSHO-RSP) to the terminal that includes information of the target
base station 230 that has accepted the entry request of the terminal 210 and an entry
limit timer TLV to inform the terminal of prohibition of entry to the serving base
station 220 for a predetermined time.
[0037] The terminal 210 that has received the base station handover response message (e.g.,
MOB_BSHO-RSP) recognizes the target base station 230 that has accepted the entry request
of the terminal 210 and simultaneously confirms the entry limit timer TLV to recognize
that entry to the serving base station 220 is prohibited for the predetermined time
(step 209). Thereafter, once the terminal 210 decides to initiate handover to the
target base station 230, the terminal 210 transmits a handover indication message
(e.g., MOB_HO-IND) to inform the serving base station 220 that handover to the target
base station 230 is to be performed (step 211).
[0038] The serving base station 220 that has received the handover indication message (e.g.,
MOB_HO-IND) provides information of the terminal 210 to the target base station 230
(step 213). For example, the information of the terminal 210 may include information
of service in use and ability information of the terminal 210. Once the target base
station 230 receives the information of the terminal 210, the terminal 210 and the
target base station 230 exchange access procedure messages and initiates access (step
215).
[0039] Once the process illustrated in FIG. 2 have been completed, the terminal 210 does
not try entry to the serving base station 220 if the predetermined time confirmed
in step 209 has not expired, even if the serving base station 220 has been considered
for handover. In other words, when the predetermined time has not lapsed, the terminal
210 suspends handover to the serving base station 220. Though only one target base
station is illustrated as a target base station candidate in FIG. 2 for convenience,
a plurality of target base station candidates may exist.
[0040] FIG. 3 illustrates a block diagram of a base station in a broadband wireless communication
system according to an exemplary embodiment of the present invention.
[0041] As shown in FIG. 3, the base station includes an RF receiver 302, an OFDM demodulator
304, a subcarrier demapper 306, a symbol demodulator 308, a decoder 310, a ranging
code detector 312, a message reader 314, an MAC controller 316, a message generator
318, an encoder 320, a symbol modulator 322, a subcarrier mapper 324, an OFDM modulator
326, and an RF transmitter 328.
[0042] The RF receiver 302 down-converts a radio frequency (RF) signal received through
an antenna into a baseband signal. The OFDM demodulator 304 classifies a signal provided
by the RF receiver 302 on an OFDM symbol basis, removes a cyclic prefix (CP), and
restores complex symbols mapped to a frequency domain through a fast Fourier transform
(FFT) operation. The subcarrier demapper 306 extracts complex symbols mapped to the
frequency domain on a process basis. For example, the subcarrier demapper 306 extracts
signals mapped to a ranging subcarrier and provides the extracted signals to the ranging
code detector 312. The symbol demodulator 308 demodulates complex symbols and converts
the demodulated complex signals into a bit stream. The decoder 310 channel-decodes
the bit stream to restore an information bit stream.
[0043] The ranging code detector 312 detects a ranging code transmitted by a terminal. That
is, the ranging code detector 312 detects which ranging code has been transmitted
by performing a correlation operation on signals mapped to a ranging subcarrier and
ranging codes prescribed in advance.
[0044] The message reader 314 reads an MAC management message received from a terminal.
For example, the message reader 314 reads a ranging request message (e.g., RNG-REQ)
from a terminal for entry into a network to confirm the terminal intending to enter
the network. Also, the message reader 314 confirms target base station candidates
by reading a handover request message (e.g., MOB_MSHO-REQ) from a terminal and confirms
a target base station to which information of the terminal should be provided by reading
a handover indication message (e.g., MOB_HO-IND) that includes information of the
target base station determined by the terminal.
[0045] The MAC controller 316 controls overall functions of the MAC layer of the base station.
For example, when a terminal tries initial ranging, the MAC controller 316 determines
whether to allow entry of the terminal on the basis of available wireless resources
and available services, for example. Also, when a terminal requests handover, the
MAC controller 316 confirms with a target base station as to whether the handover
of the terminal is acceptable.
[0046] Particularly, in accordance with the present invention, the MAC controller 316 determines
whether to prohibit entry attempts by the terminal. In this case, entry (i.e., access
to a base station) may be by initial ranging or handover. For example, in the case
where a terminal is denied entry to the base station through initial ranging, the
MAC controller 316 prohibits the denied terminal from trying entry (i.e., initial
ranging) to the base station for a predetermined time. In the case where a terminal
performs handover to an adjacent base station, the MAC controller 316 prohibits the
terminal performing the handover from trying entry (i.e., handover) to the base station
for a predetermined time.
[0047] The message generator 318 generates an MAC management message to be transmitted to
a terminal. For example, the message generator 318 generates a ranging response message
(e.g., RNG-RSP), which is a response to an entry attempt by the terminal, a base station
handover response message (e.g., MOB_BSHO-RSP), which is a response to a handover
request from the terminal, and a base station handover request message (e.g., MOB-BSHO-REQ)
to request the terminal to perform a handover. Particularly, in accordance with the
present invention, the message generator 318 generates a parameter representing prohibition
of entry attempts to the base station for a predetermine time, such as an MAC management
message including an entry limit timer TLV. For example, the entry limit timer TLV
may be included in the ranging response message (e.g., RNG-RSP), the base station
handover response message (e.g., MOB_BSHO-RSP), or the base station handover request
message (e.g., MOB_BSHO-REQ) depending on entry attempt. The entry limit timer TLV
may be configured as shown in Table 1.
[0048] When the MAC management message, the ranging response message (e.g., RNG-RSP), for
example, the ranging response message (e.g., RNG-RSP) may include at least one of
a parameter representing denial of entry (e.g., ranging status TLV), a parameter representing
prohibited time period for entry (e.g., entry limit timer TLV), and a parameter indicating
a different frequency (FA) (e.g., downlink frequency override TLV) through which an
entry is recommended. When the MAC management message is the base station handover
response message (e.g., MOB_BSHO-RSP) or the base station handover request message
(e.g., MOB_BSHO-REQ), the base station handover response/request message (e.g., MOB_BSHO-RSP
or MOB_BSHO-REQ) may include at least one of a parameter representing prohibited time
period for entry (e.g., entry limit timer TLV) and a parameter identifying target
base station candidate(s) that can accept a handover.
[0049] The encoder 320 channel-codes an information bit stream. The symbol modulator 322
modulates the channel-coded bit stream and converts the modulated bit stream into
complex symbols. The subcarrier mapper 324 maps the complex symbols to a frequency
domain. The OFDM modulator 326 converts the complex symbols mapped to the frequency
domain into signals in a time domain through the inverse fast Fourier transform (IFFT)
operation and inserts a CP to form an OFDM symbol. The RF transmitter 328 up-converts
a baseband signal into an RF signal and transmits the RF signal through the antenna.
[0050] FIG. 4 illustrates a block diagram of a terminal in a broadband wireless communication
system according to an exemplary embodiment of the present invention.
[0051] As shown in FIG. 4, the terminal includes an RF receiver 402, an OFDM demodulator
404, a subcarrier demapper 406, a symbol demodulator 408, a decoder 410, a signal
strength measuring unit 412, a message reader 414, an MAC controller 416, a message
generator 418, an encoder 420, a symbol modulator 422, a subcarrier mapper 424, an
OFDM modulator 426, and an RF transmitter 428.
[0052] The RF receiver 402 down-converts an RF signal received through an antenna into a
baseband signal. The OFDM demodulator 404 classifies a signal provided from the RF
receiver 402 on an OFDM symbol basis, removes a CP, and restores complex symbols mapped
to a frequency domain through the FFT operation. The subcarrier demapper 406 extracts
complex symbols mapped to the frequency domain on a process basis. For example, while
the terminal scans a base station for network entry or handover, the subcarrier demapper
406 extracts a signal for scanning, e.g., a preamble signal, and provides the preamble
signal to the signal strength measuring unit 412. The symbol demodulator 408 demodulates
complex symbols and converts the demodulated complex symbols into a bit stream. The
decoder 410 restores an information bit stream by channel-decoding the bit stream.
[0053] The signal strength measuring unit 412 measures strength of a signal received from
a base station. For example, the received signal strength can be expressed by received
signal strength indication (RSSI), signal-to-noise ratio (SNR), signal-to-interface-and-noise
ratio (SINR), carrier-to-interference-and-noise ratio (CINR), etc.
[0054] The message reader 414 reads an MAC management message received from a base station.
For example, the message reader 414 confirms whether initial ranging is allowed by
reading a ranging response message (e.g., RNG-RSP), which is a response to an initial
ranging request, confirms a target base station that can accept a handover by reading
a base station handover response message (e.g., MOB_BSHO-RSP), which is a response
to a handover request, and confirms an acceptable target base station with respect
to a handover by reading a base station handover request message (e.g., MOB-BSHO-REQ)
to request the terminal to perform a handover. Particularly, in accordance with the
present invention, the message reader 414 confirms a parameter representing prohibition
of entry attempts to a base station for a predetermined time, that is, the entry limit
timer TLV. In this case, entry (i.e., access to a base station) may be by initial
ranging or handover. For example, the entry limit timer TLV may be included in the
ranging response message (e.g., RNG-RSP), the base station handover response message
(e.g., MOB_BSHO-RSP), or the base station handover request message (e.g., MOB_BSHO-REQ)
depending on the entry attempt. The entry limit timer TLV may be configured as shown
in Table 1.
[0055] The MAC controller 416 controls overall functions of the MAC layer of the terminal.
For example, when the terminal tries initial ranging, the MAC controller 416 controls
the terminal to generate and transmit a ranging request message (e.g., RNG-REQ). Also,
when the terminal requests a handover, the MAC controller 416 controls the terminal
to generate and transmit a handover request message (e.g., MOB_MSHO-REQ) including
information of collected target base station candidates. The MAC controller 416 controls
the terminal depending on allowance/denial status included in a ranging response message
(e.g., RNG-RSP), which is a response to an initial ranging attempt. For example, in
the case where an entry to a base station through initial ranging is rejected, the
MAC controller 416 controls the terminal to scan for other base stations to enter
the network. In the case of handover, the MAC controller 416 controls the operation
of the terminal depending on information of target base station candidates that can
accept a handover included in a base station handover response message (e.g., MOB_BSHO-RSP),
which is a response to a handover request from the terminal. That is, the MAC controller
416 controls the terminal to select one of the target base station candidates that
can accept a handover and transmit a handover indication message (e.g., MOB_HO-IND)
to inform the selected target base station.
[0056] Particularly, in accordance with the present invention, when an entry limit timer
TLV is detected in a received MAC management message, the MAC controller 416 prohibits
entry attempts to the base station that has transmitted the MAC management message
for a predetermined time designated by the entry limit timer TLV, that is, until the
timer has expired. For example, in the case where the entry limit timer TLV is included
in the ranging response message (e.g., RNG-RSP), the MAC controller 416 prohibits
entry attempts to the base station that has transmitted the ranging response message
(e.g., RNG-RSP) for a predetermined time. That is, when the base station that has
transmitted the ranging response message is selected again as a result of scanning
for base stations in order to enter a network, the MAC controller 416 controls the
terminal to try initial ranging to one of the base stations other than the base station
that has transmitted the ranging response message if the predetermined time has not
expired. When the entry limit timer TLV is included in the base station handover response
message (e.g., MOB_BSHO-RSP) or the base station handover request message (e.g., MOB_BSHO-REQ),
the MAC controller 416 prohibits entry attempts, i.e., attempts for handover, to the
base station that has transmitted the base station handover response/request message
(e.g., MOB_BSHO-RSP or MOS_BSHO-REQ) for a predetermined time.
[0057] The message generator 418 generates an MAC management message transmitted to a base
station. For example, the message generator 418 generates a handover request message
(e.g., MOB_MSHO-REQ) to request a handover, a handover indication message (e.g., MOB_HO-IND)
that includes information of a selected target base station for handover, and a ranging
request message (e.g., RNG-REQ) to initiate initial ranging.
[0058] The encoder 420 channel-codes an information bit stream. The symbol modulator 422
modulates the channel-coded bit stream and converts the modulated bit stream into
complex symbols. The subcarrier mapper 424 maps the complex symbols to a frequency
domain. The OFDM modulator 426 converts the complex symbols mapped to the frequency
domain into signals in a time domain through the IFFT operation, and inserts a CP
to form an OFDM symbol. The RF transmitter 428 up-converts a baseband signal into
an RF signal, and transmits the RF signal through the antenna.
[0059] FIG. 5 illustrates the operating procedure of a base station in a broadband wireless
communication system according to an exemplary embodiment of the present invention.
[0060] As shown to FIG. 5, in step 501, the base station confirms whether a terminal performs
handover to an adjacent base station, or whether an initial network entry of the terminal
is rejected. Specifically, when the terminal performs the handover, the base station
confirms whether at least one of target base station candidates can accept the handover
of the terminal. Alternatively, when an entry request of the terminal through initial
ranging occurs, the base station confirms whether entry is rejected because of resource
shortage or service unavailable.
[0061] In step 503, once the terminal performs handover to an adjacent base station or the
initial network entry of the terminal is rejected, the base station determines to
prohibit the terminal from trying entry to the base station for a predetermined time.
Here, entry (i.e., access to the base station) may be by initial ranging or handover.
It is to be understood that the length of time for prohibition (i.e., the predetermined
time) may vary depending on the specific instance without departing from the scope
of the present invention.
[0062] In step 505, once it has been determined to prohibit the terminal from trying entry,
the base station generates a parameter representing prohibition of entry attempts,
that is, an MAC management message including an entry limit timer TLV. For example,
the entry limit timer TLV may be included in the ranging response message (e.g., RNG-RSP),
the base station handover response message (e.g., MOB_BSHO-RSP), or the base station
handover request message (e.g., MOB_BSHO-REQ) depending on the attempted entry. The
entry limit timer TLV may be configured as shown in Table 1.
[0063] When the MAC management message is the ranging response message (e.g., RNG-RSP),
the ranging response message may include at least one of a parameter representing
denial of entry (e.g., ranging status TLV), a parameter representing prohibited time
period for entry (e.g., an entry limit timer TLV), and a parameter indicating a different
frequency (FA) (e.g., downlink frequency override TLV) through which an entry is recommended.
When the MAC management message is the base station handover response message (e.g.,
MOB_BSHO-RSP) or the base station handover request message (e.g., MOB_BSHO-REQ), the
base station response/request message (e.g., MOB_BSHO-RSP or MOB_BSHO-REQ) may include
at least one of a parameter representing prohibited time period for entry (e.g., entry
limit timer TLV) and a parameter identifying target base station candidate(s) that
can accept a handover.
[0064] In step 507, the base station transmits the MAC management message generated in step
505 to the appropriate terminal.
[0065] FIG. 6 illustrates the operating procedure of a terminal in a broadband wireless
communication system according to an exemplary embodiment of the present invention.
[0066] As shown to FIG. 6, in step 601, the terminal confirms whether an MAC management
message is received from a base station.
[0067] In step 603, when the MAC management message is received, the terminal confirms whether
a parameter representing prohibition of entry attempts (i.e., an entry limit timer
TLV) is included in the MAC management message by reading the MAC management message.
Here, entry (i.e., access to a base station) may be by initial ranging or handover.
For example, the entry limit timer TLV may be included in a ranging response message
(e.g., RNG-RSP), a base station handover response message (e.g., MOB_BSHO-RSP), or
a base station handover request message (e.g., MOB_BSHO-REQ) depending on the attempted
entry. The entry limit timer TLV may be configured as shown in Table 1. That is, the
terminal confirms the existence of entry limit timer TLV by reading the ranging response
message (e.g., RNG-RSP), the base station handover response message (e.g., MOB_BSHO-RSP),
and the base station handover request message (e.g.., MOB_BSHO-REQ). If the entry
limit timer TLV is not detected in the MAC management message, the terminal performs
step 607 (described below).
[0068] When the entry limit timer TLV is detected, in step 605, the terminal sets prohibition
of entry attempts to the base station that has transmitted the MAC management message
for a predetermined time, that is, until expiration of a timer. Accordingly, the terminal
does not try entry to the base station when the predetermined time has not expired
even if the base station is selected as an optimum base station after scanning for
network entry or for handover.
[0069] Subsequently, in step 607, the terminal performs MAC layer operation according to
the received MAC management message. For example, when the MAC management message
is a ranging response message (e.g., RNG-RSP) and ranging status TLV is set to "abort,"
the terminal scans for base stations to enter the network. Alternatively, when the
MAC management message is a base station handover response/request message (e.g.,
MOB_BSHO-RSP or MOB_BSHO-REQ), the terminal selects a target base station to which
handover is to be made and transmits information of the selected target base station
to a serving base station.
[0070] Accordingly, unnecessary entry attempts and unnecessary execution of entry procedures
by a terminal in a broadband wireless communication system are prevented due to prohibition
of re-entry attempts using a parameter representing a time period prohibiting entry
attempts when initial ranging is rejected or handover of the terminal.
[0071] Although the invention has been shown and described with reference to certain exemplary
embodiments thereof, it will be understood by those skilled in the art that various
changes in form and details may be made therein without departing from the spirit
and scope of the invention as defined by the appended claims. Therefore, the scope
of the present invention should not be limited to the above-described embodiments
but should be determined by not only the appended claims but also the equivalents
thereof.
1. A circuit, comprising:
a controller to determine whether to prohibit entry of an end unit to a base station
in a wireless communication network, the controller configured to process a media
access control (MAC) management message that includes a timer value, the timer value
designating a time period during which entry is prohibited.
2. A method, comprising:
determining whether to prohibit entry of an end unit to a base station in a wireless
communication network; and
processing a media access control (MAC) management message that includes a timer value,
the timer value designating a time period during which entry is prohibited.
3. The circuit of claim 1 or the method of claim 2, wherein entry is any one of initial
ranging and handover.
4. The circuit or the method as claimed in any one of claim 1 to 3, wherein the MAC management
message is a ranging response message in response to an initial ranging request from
the end unit.
5. The circuit or the method as claimed in any one of claim 1 to 4, wherein the ranging
response message includes a ranging status to indicate acceptance/rejection of the
initial ranging request.
6. The circuit or the method as claimed in any one of claim 1 to 5, wherein the ranging
response message includes frequency allocation (FA) indicative of a different frequency
through which entry is recommended.
7. The circuit or the method as claimed in any one of claim 1 to 6, wherein the MAC management
message is a handover response message in response to a scanning of one or more target
base stations for the handover of the end unit.
8. The circuit or the method as claimed in any one of claim 1 to 7, wherein the handover
response message includes information of one or more target base station candidates
able to accept handover of the end unit.
9. The circuit or the method as claimed in any one of claim 1 to 8, wherein the MAC management
message includes a handover request message for instructing the end unit to perform
the handover to a target base station.
10. The circuit as claimed in any one of claim 1 to 9, wherein the controller is included
in the end unit.
11. The circuit as claimed in any one of claim 1 to 10, wherein the end unit further includes
a timer to determine the time period during which entry is prohibited.
12. The circuit as claimed in any one of claim 1 to 11, wherein the end unit suspends
further attempts of initial ranging to the base station after initial ranging to the
base station has been rejected until the time period has expired.
13. The circuit as claimed in any one of claim 1 to 12, wherein the end unit suspends
further attempts of handover to the base station until the time period has expired.
14. The circuit as claimed in any one of claim 1 to 13, wherein the controller is included
in the base station.
15. The circuit as claimed in any one of claim 1 to 14, wherein the controller transmits
the timer value to the end unit after initial ranging by the base station has been
rejected so that further attempts of initial ranging by the end unit to the base station
is prohibited until the time period has expired.
16. The circuit as claimed in any one of claim 1 to 15, wherein the controller transmits
the timer value to the end unit after initiation of handover so that further attempts
of handover by the end unit to the base station is prohibited until the time period
has expired.
17. The method as claimed in any one of claim 1 to 9, wherein the processing includes
reception of the MAC management message by the end unit from the base station.
18. The method as claimed in any one of claim 1 to 9 and 17, the method further comprising
suspending further attempts of initial ranging to the base station by the end unit
after initial ranging to the base station has been rejected until the time period
has expired.
19. The method as claimed in any one of claim 1 to 9, 17 and 18, the method further comprising
suspending further attempts of handover to the base station by the end unit until
the time period has expired.
20. The method as claimed in any one of claim 1 to 9 and 17 to 19, wherein the processing
includes transmission of the MAC management message by the base station to the end
unit.
21. The method as claimed in any one of claim 1 to 9 and 17 to 20, wherein the processing
includes transmitting the timer value to the end unit after initial ranging by the
base station has been rejected so that further attempts of initial ranging by the
end unit to the base station is prohibited until the time period has expired.
22. The method as claimed in any one of claim 1 to 9 and 17 to 21, wherein the processing
includes transmitting the timer value to the end unit after initiation of handover
so that further attempts of handover by the end unit to the base station is prohibited
until the time period has expired.